As the visible near-infrared broadband absorber plays an important role in numerous different new fields, more and more ultra-broadband absorbers have been developed in recent years based on extensive study. In recent years, researchers have proposed various near-infrared electromagnetic wave absorbers with artificial electromagnetic structure. Among them, Chen et al. have produced gold nanorod in random arrangement on the metal substrate coated with a dielectric layer by means of droplet evaporation, and thereby realized high absorption at the near-infrared broadband of 900 nm-1600 nm (Near-infrared broadband absorber with film-coupled multilayer nanorods, Optics Lett. 38, 2247-2249 (2013)); Zhou et al. have realized high absorption at near-infrared broadband by preparing a conical structure of multilayer alternating medium/metal by means of lateral deposition (Experiment and Theory of the Broadband Absorption by a Tapered Hyperbolic Metamaterial Array, ACS Photonics 1, 618-624 (2014)); Ji et al. have proposed a structure comprised of alternating accumulation of metallic particles and silicon oxide film on the surface of silver reflector, and thereby realized high absorption above 96% on average at the waveband of 300nm-1100nm (Plasmonic broadband absorber by stacking multiple metallic nanoparticle layers, Appl. Phys. Lett. 106, 161107 (2015)).
However, the aforesaid preparation methods are complicated and time-consuming with high cost, and thus are not suitable for large-scale mass production.
Relevant available literatures are stated as follows:
Chinese Patent Application No. 201510163240.8 has disclosed an ultra-broadband absorber of meta-material based on the cascade architecture; such absorber comprises 9 medium layers and 9 metal layers; the medium layer and metal layer 1-3 comprise cylinders of the same diameter; the medium layer and metal layer 4-6 comprise cylinders of the same diameter; the medium layer and metal layer 7-9 comprise cylinders of the same diameter; and overall structure of such absorber is relatively complicated with higher requirements on the incidence angle.
Chinese Patent Application No. 201410020841.9 has disclosed a structure for visible near-infrared broadband absorption film which produces a metal film layer and medium film layer on any substrates by means of vapor deposition and liquid deposition in proper sequence; wherein, thickness of the metal film layer and the medium film layer is 80 nm-1 μm and 1 nm-200 nm respectively; in the disordered distribution layer of metallic particles, average height of the equivalent film layer is 5 nm-100 nm with average particle size up to 10 nm-200 nm; and surface coverage of metallic particles is 3%-90%. The structure is relatively simple but its absorption is unsatisfactory.
Chinese Patent Application No.201110410712.7 has disclosed a selective solar absorption coat which comprises a two-layer or three-layer structure: the first layer is a polished stainless steel substrate; the second layer is a Cu1.5Mn1.5O4 composite oxide absorption layer; and the third layer is an anti-reflection layer composed of TiO2 film from bottom to top. The absorption of the coating below 0.9 and the preparation process is complicated.